Compressor housing for supercharger and method for manufacturing the same

Abstract

In a compressor housing, a scroll piece includes a cylindrical intake port forming section, a scroll wall surface forming section that forms an air-intake side wall surface of a discharge scroll chamber, and a scroll outer circumferential section that covers an outer circumferential side of the discharge scroll chamber. A shroud piece of the housing includes a cylindrical shroud press fitted section press fitted into the intake port forming section, and a shroud wall surface forming section that forms an inner circumferential side wall surface of the discharge scroll chamber and also forms a shroud surface that opposes an impeller and a diffuser surface. An outer circumferential annular piece of the housing includes an outer circumferential annular press fitted section press fitted inside the scroll outer circumferential section, and an outer circumferential annular wall surface forming section that forms an outer circumferential side wall surface of the discharge scroll chamber.

The invention claimed is: 
     
       1. A compressor housing for a supercharger, which is configured to house an impeller with a plurality of blades, and includes an intake port that takes in air toward the impeller, and a discharge scroll chamber that is formed in a circumferential direction at an outer circumferential side of the impeller, and that guides the air discharged from the impeller to outside, comprising:
 a scroll piece including a cylindrical intake port forming section that forms the intake port, a scroll wall surface forming section that forms an air-intake side wall surface of the discharge scroll chamber, and a scroll outer circumferential section that covers an outer circumferential side of the discharge scroll chamber; 
 a shroud piece including a cylindrical shroud press fitted section that is press fitted into the intake port forming section of the scroll piece, and a shroud wall surface forming section that forms an inner circumferential side wall surface of the discharge scroll chamber, and that forms a shroud surface opposing the impeller and a diffuser surface that extends from the shroud surface toward the discharge scroll chamber; and 
 an outer circumferential annular piece including an outer circumferential annular press fitted section that is press fitted into the scroll outer circumferential section of the scroll piece, and an outer circumferential annular wall surface forming section that forms an outer circumferential side wall surface of the discharge scroll chamber, 
 wherein the shroud piece includes a positioning section that makes contact in an axial direction with a contacting section of the scroll piece such that the outer circumferential annular piece and the scroll piece maintain a gap from one another in the axial direction. 
 
     
     
       2. The compressor housing for a supercharger according to  claim 1 , wherein the compressor housing is used in the supercharger in which a back plate opposing the diffuser surface of the shroud wall surface forming section of the shroud piece and a bearing housing that axially supports a rotation shaft of the impeller are integrally formed. 
     
     
       3. A method of manufacturing the compressor housing for a supercharger according to  claim 1  or  2 , the method comprising:
 forming the scroll piece and an integral piece that integrally includes parts that are to be the shroud piece and the outer circumferential annular piece by die casting, respectively; 
 press fitting the shroud press fitted section that constitutes a part of the integral piece into the intake port forming section of the scroll piece, and press fitting the outer circumferential annular press fitted section that constitutes a part of the integral piece into the scroll outer circumferential section of the scroll piece; and 
 cutting the integral piece subsequent to the press-fitting, and separating the integral piece into the shroud piece and the outer circumferential annular piece, 
 wherein in the press-fitting, the positioning section, which is formed in the part of the integral piece which is to be the shroud piece, is brought into contact in an axial direction with the contacting section formed in the scroll piece such that the part of the integral piece which is to be the outer circumferential annular piece is spaced apart from the scroll piece by the gap in the axial direction. 
 
     
     
       4. The method of manufacturing the compressor housing for a supercharger according to  claim 3 , wherein in the press-fitting, a press-fitting fastening margin between the scroll outer circumferential section of the scroll piece and the outer circumferential annular press fitted section that constitutes the part of the integral piece is made smaller than a press-fitting fastening margin between the intake port forming section of the scroll piece and the shroud press fitted section that constitutes the part of the integral piece. 
     
     
       5. The compressor housing for a supercharger according to  claim 1 , wherein the contacting section is formed at a bottom portion of the intake port forming section of the scroll piece and the positioning section is formed at a connecting portion between the shroud press fitted section of the shroud piece and the shroud wall surface forming section. 
     
     
       6. The compressor housing for a supercharger according to  claim 1 , wherein the contacting section is formed at an axial direction intermediate position of the intake port forming section and the positioning section is formed at a tip end portion of the shroud press fitted section.